Consolidated Statements of Cash Flows (USD $)
3 Months Ended
Mar. 31, 2015
Mar. 31, 2014
Cash flows from operating activities    
Net loss $ (11,834,000) $ (6,144,000)
Adjustments to reconcile net loss to net cash used in operating activities    
Depreciation and amortization 3,433,000 3,070,000
Non-cash interest and other expense 1,883,000 2,528,000
Stock-based compensation expense 5,305,000 4,360,000
Provision for bad debts 328,000 891,000
Changes in operating assets and liabilities:    
Accounts receivable 3,461,000 (4,503,000)
Inventories (6,966,000) (985,000)
Deferred revenue 313,000 (288,000)
Prepaid expenses and other assets 384,000 (904,000)
Accounts payable, accrued expenses and other current liabilities (59,000) 917,000
Other long-term liabilities 264,000 41,000
Net cash used in operating activities (3,488,000) (1,017,000)
Cash flows from investing activities    
Purchases of property and equipment (4,346,000) (2,157,000)
Net cash used in investing activities (4,346,000) (2,157,000)
Cash flows from financing activities    
Principal payments of capital lease obligations (1,193,000) (618,000)
Proceeds from issuance of common stock 4,876,000 3,561,000
Payment of withholding taxes in connection with vesting of restricted stock units (1,434,000) (3,882,000)
Net cash provided by (used in) financing activities 2,249,000 (939,000)
Net decrease in cash and cash equivalents (5,585,000) (4,113,000)
Cash and cash equivalents, beginning of period 151,193,000 149,727,000
Cash and cash equivalents, end of period 145,608,000 145,614,000
Non-cash investing and financing activities    
Purchases of property and equipment under capital lease 5,721,000 0
3.75% Convertible Notes    
Adjustments to reconcile net loss to net cash used in operating activities    
Non-cash interest and other expense $ 0 $ 2,800,000